Optical gas detectors are well known. In particular, such detectors are used in the design of, for example, carbon dioxide and hydrocarbon gas detectors. In this case, infrared radiation emitted by a source can pass through a chamber containing the gas under test, where some of the infrared radiation will be absorbed by the gas. Absorption by a specific gas is a function of the wavelength of the infrared radiation. Therefore, by careful selection of an appropriate optical band-pass filter at a detector, it is possible to determine the presence of a specific gas. In addition to sensing carbon dioxide hydrocarbon gases, ozone detectors also use radiation. In this case, the radiation is in the ultraviolet range.
Air disinfection devices are available on the market and include air cleaners that filter airborne toxins, dust mites, and pet dander from the air. Some air purifiers can remove or reduce smoke, dust, and pollen from an environment, as well as reduce an amount of bacteria in the air. Unfortunately, reducing viral levels in the air is difficult with a conventional filter (such as a HEPA filter, for example), as viruses are not well captured by the filter due to their small size. Ultraviolet air disinfection devices have been utilized in the past for disinfecting air from viruses. Unfortunately, a problem with ultraviolet air purifiers is that they do not provide sufficient radiation levels in the air to get air well purified. For example, the ultraviolet light can get absorbed by the chamber walls containing disinfection gases, resulting in a relatively low efficiency of ultraviolet disinfection chambers. To date, the best reflective metallic material available for ultraviolet reflection constitutes well-polished aluminum, which is only 90% reflective. In order to increase an efficiency of such chambers, the chambers are required to be large in size making their usage difficult in a typical office environment.
In addition to air disinfection, ultraviolet emitters can be effectively used to disinfect liquids, such as water, and have found their use in various water treatment facilities. Water treatment using ultraviolet radiation offers many advantages over other forms of water treatment, such as chemical treatment. For example, treatment with ultraviolet radiation does not introduce additional chemical or biological contaminants into the water. Furthermore, ultraviolet radiation provides one of the most efficient approaches to water decontamination since there are no microorganisms known to be resistant to ultraviolet radiation, unlike other decontamination methods, such as chlorination. Ultraviolet radiation is known to be highly effective against bacteria, viruses, algae, molds, and yeasts. For example, hepatitis virus has been shown to survive for considerable periods of time in the presence of chlorine, but is readily eliminated by ultraviolet radiation treatment. The removal efficiency of ultraviolet radiation for most microbiological contaminants, such as bacteria and viruses, generally exceeds 99%. To this extent, ultraviolet radiation is highly efficient at eliminating E-coli, Salmonella, Typhoid fever, Cholera, Tuberculosis, Influenza Virus, Polio Virus, and Hepatitis A Virus.
Ultraviolet radiation disinfection using mercury based lamps is a well-established technology. In general, a system for treating water using ultraviolet radiation is relatively easy to install and maintain in a plumbing or septic system. Use of ultraviolet radiation in such systems does not affect the overall system. However, it is often desirable to combine an ultraviolet purification system with another form of filtration since the ultraviolet radiation cannot neutralize chlorine, heavy metals, and other chemical contaminants that may be present in the water. Various membrane filters for sediment filtration, granular activated carbon filtering, reverse osmosis, and/or the like, can be used as a filtering device to reduce the presence of chemicals and other inorganic contaminants.
Mercury lamp-based ultraviolet radiation disinfection has several shortcomings when compared to deep ultraviolet (DUV) light emitting device (LED)-based technology, particularly with respect to certain disinfection applications. For example, in rural and/or off-grid locations, it is desirable for an ultraviolet purification system to have one or more of various attributes such as: a long operating lifetime, containing no hazardous components, not readily susceptible to damage, requiring minimal operational skills, not requiring special disposal procedures, capable of operating on local intermittent electrical power, and/or the like. Use of a DUV LED-based solution can improve one or more of these attributes as compared to a mercury vapor lamp-based approach. For example, in comparison to mercury vapor lamps, DUV LEDs: have substantially longer operating lifetimes (e.g., by a factor of ten); do not include hazardous components (e.g., mercury), which require special disposal and maintenance; are more durable in transit and handling (e.g., no filaments or glass); have a faster startup time; have a lower operational voltage; are less sensitive to power supply intermittency; are more compact and portable; can be used in moving devices; can be powered by photovoltaic (PV) technology, which can be installed in rural locations having no continuous access to electricity and having scarce resources of clean water; and/or the like.